This invention relates to an airbag module and actuator for selectively diverting inflation gases away from the interior of an airbag.
Airbag modules comprise an airbag and an airbag inflator. When triggered by a crash detection system, the airbag inflator rapidly provides gas to inflate the airbag. The inflated airbag then serves as a cushion against injury for a vehicle occupant.
The location of the vehicle occupant with respect to the airbag may affect the effectiveness of the airbag as a cushion. If the vehicle occupant is too close to the airbag, full inflation of the airbag may result in less than optimal cushioning of any impact. Accordingly, it is desirable to inflate the airbag to less than full capacity when the vehicle occupant is too close to the airbag.
Systems exist that detect the location of the vehicle occupant. When these systems sense that the vehicle occupant is too close to the airbag, they inflate the airbag to less than full capacity. A dual-stage inflator serves to inflate the airbag in this way. The inflator""s first stage partially inflates the airbag, while the second stage, if triggered, fills the airbag to a maximum level.
However, a dual-stage inflator is generally more expensive than a single-stage inflator. It would be desirable to be able to provide a virtually infinite variety of inflation levels. As an alternative to a dual-stage inflator, the present invention provides an airbag module that vents inflation gas away from the airbag when the airbag has reached an appropriate inflation level.
The airbag module of the present invention has a flap that moves from an open position that permits inflation gas to inflate the airbag to a closed position in which the inflation gas is deflected away from the opening in the airbag. In this way, the airbag module permits a greater variety of inflation levels for the airbag without adding significant cost to the manufacture of the airbag module. An actuator moves the flap from an open position to a closed position when signaled by a control unit that the airbag has reached an appropriate inflation level.
The actuator comprises a propellant that is ignited when the actuator is signaled to do so. Upon ignition the propellant generates a gas that rapidly expands to generate a force that moves the flap from the open position to the closed position. However, when ignited the propellant may emit a flash of light and discharge residual particles into the passenger compartment. While this light and these particles are by no means dangerous, during a vehicle crash they may alarm a vehicle occupant.
A need therefore exists for an airbag module and actuator that suppresses these undesirable effects.
Like existing airbag modules, the airbag module of the present invention comprises an airbag inflatable through an opening in the airbag. An inflator generates an inflation gas that passes through the opening in the airbag during deployment. Unlike known systems, the invention uses a flap that opens and closes the opening in the airbag. Typically, the flap is held in the open position to permit inflation gas to pass through the airbag during airbag deployment. When the airbag has reached an appropriate inflation level, a propellant discharges and moves the flap between the open position to the closed position. To prevent both light and residual particles from escaping into the passenger compartment, a hood covers the space where the propellant discharges.
The hood may comprise a hollow body that surrounds the discharge space. The propellant may be located in hollow body. By surrounding the area of propellant discharge, the hollow body shields the passenger compartment from light and particles generated by the propellant.
In addition, a piston may slide within the hollow body to increase the force of the propellant and even collide with the flap to close the opening in the airbag. The piston may have two positions: an actuated position following discharge and an unactuated position prior to discharge. In the unactuated position, the piston protrudes very little, if at all, out of the hollow body. On the other hand, in the actuated position, the piston extends from this position to actually contact the flap and thereby impart the momentum of the piston, and the pressure of the expanding gas to move the flap from the open position to the closed position.
The hollow body may have two pieces, an upper housing and a lower housing, and may further have a retaining lip to keep the piston from launching out of the hollow body completely. Pressure build-up within the hollow body may be significant in comparison to the scale of the piston and hollow body. Accordingly, a hole may vent inflation gas out of the hollow body to relieve this pressure build-up. The hole may be located on the piston.
The propellant may have a housing as well. The housing may be fitted with electrical contacts that ignite the propellant when signaled. To ignite the propellant, current is passed through these contacts from a controller.
The airbag actuator may accordingly have a propellant stored in a propellant housing. The actuator has a hollow body that receives the propellant and propellant housing in one end and receives a piston in the other end. Light and particles from the propellant reaction are then largely contained within the hollow body between the propellant housing and the piston. A hole in the piston reduces pressure build-up within the hollow body without allowing significant amounts of light and particles to escape during the reaction.